The present invention is related to a method and an apparatus for rotating a component of a wind energy plant by traversing an adjustment device. Adjustment devices are used in wind energy plants for rotating various components. A known example is the blade pitch angle adjustment device, by which the blade pitch angle of the rotor blades of the plant is adjusted. By doing so, the rotor blades are rotated around their longitudinal axes. Such a blade pitch angle adjustment device is usually a part of a so-called pitch regulation. Another also known example are azimuth adjustment devices, by which the machine house of the wind energy plant is rotated around the longitudinal axis of the tower. Such azimuth adjustment devices form a part of a so-called azimuth system of the wind energy plant, which has the objective to orient the machine house or the nacelle of the wind energy plant, respectively, at optimum to the wind direction, and to untwist the lines running between the tower of the plant and the machine house (the cable loop) from time to time. Such azimuth systems are known from Erich Hau, Windkraftanlagen, Springer Verlag, 3th edition, page 309ff., for instance, the entire contents of which is incorporated herein by reference.
Normally, the adjustment devices feature one or more adjustment drives. In azimuth adjustment drives, for instance, a planetary gearbox, a motor, an electric motor for instance, and a braking device, an electric brake for instance, is usually provided. In this, the output gear pinion of the gearbox meshes with the toothing of an azimuth swing bearing. The torques and the rotational speeds are geared up or down via toothings in the gearboxes. In the operation, the adjustment devices are exposed to changing dynamic loads, from the attacking wind in particular. In this, elasticities in the drives are generated, as a consequence of which the adjustment devices cannot instantaneously react on the exterior loads, or cannot suddenly apply a demanded driving torque, respectively. The elasticity of gearboxes depends on the tooth clearance of the individual tooth engagements. The more tooth engagements are used for the gearbox transformation, and the greater the respective tooth clearance is, the greater is the elasticity of the gearbox. In azimuth drives for instance, at a tightening up to the rated torque, the elasticity can amount up to ten rotations of the fast shaft of a four-step planetary gearbox. In the traversing of the adjustment devices, small partial moments are conventionally also distributed to the swing bearing or to the braking device used for holding the azimuth system, respectively, to the brake calipers in particular.
The driving torque of the adjustment drives is dimensioned for cases of high load, wherein the adjustment device experiences a change of the rotational speed when these cases of load are exceeded, when it is braked down or accelerated in particular. Furthermore, in the changes of the operation condition, namely holding after travelling and travelling after holding, load takeovers have to be realised which can lead to a decrease of the common driving/holding moment. These dropdowns of the moment can have various reasons:
When the wind loads require a change between driving and braking loads, the driving torque of the adjustment drives drops down, because the drives must retorque themselves anew over several rotations due to the existing elasticities. In addition, the adjustment drives, the azimuth drives in particular, can have a regulation imprecision when they are electrically triggered by soft start devices or frequency converters at low rotational speeds, in the starting in particular, and for this reason they may not react instantaneously to load changes. Finally, the rise of the detent torque of conventionally used brake calipers, which takes place via a wedge, may last for several seconds. Through this, the load takeover by the brake calipers is delayed for the drives.
It is known to maintain a detent torque by a braking device of the adjustment drives, for instance via a pressing force of corresponding brake calipers, so that the drives traverse against a base load. In the operation of the plant, there are cases of load in which the adjustment device is driven out of the wind or braked down by the loads. For instance, in the case of an azimuth adjustment device, the moments of the attacking loads are distributed to the partial systems azimuth drive, swing bearing and brake calipers of a braking device. For the case of a conventional azimuth system, the cases of load are listed in the following table. In this, the effect on the azimuth system by the detent torque of the brake calipers of the braking device is listed in particular:
“Load case”of theazimuthAzimuthBrakeSwingEffect to the azimuthsystemdrivecalipersbearingsystemStarting withDrivingHoldingHoldingMore difficult to startcounter-Delayed startingmoment fromThe detent torque makesthe windthe starting even moredifficultTravelling withDrivingHoldingHoldingReduced traversing speedcounter-Frequent breakdown ofmoment fromthe rated rotational speedthe windThe detent torque makesthe rotational speedbehaviour worse.Stopping withBrakingHoldingHoldingThe detent torquecounter-supports themoment fromstopping procedurethe windStarting withDrivingHoldingHoldingThe detent torquedrivingprotects againstmoment fromexceeding the ratedthe windrotational speedTravelling withDriving orHoldingHoldingThe detent torquedrivingbrakingprotects againstmoment fromfluctuations of thethe windrotational speedStopping withBrakingHoldingHoldingThe detent torquedrivingsupports themoment fromstopping procedurethe wind
A disadvantage of applying a detent torque by a braking device in the traversing of the adjustment device is increased wear of the brake, and a regular maintenance which is required through this.
From U.S. Pat. No. 5,035,575 A, the entire contents of which is incorporated herein by reference, an azimuth system of a wind energy plant is known, in which two motors of the adjustment drives are operated in opposite senses with an equal torque in the standstill of the azimuth adjustment device. Through this, a tightening of the adjustment devices in the standstill is achieved. When the azimuth system is traversed, both motors rotate then in the same sense and with the same torque. Thus, no more tightening is achieved when the adjustment device is traversed by doing so. Furthermore, from DE 103 58 486 A1, the entire contents of which is incorporated herein by reference, an azimuth drive is known for a wind energy plant which features a hydraulic device for tightening the drives. In particular, two hydraulic motors are provided in this, which engage via corresponding driving wheels in opposite rotational senses and with equal torques on the output ring gear of an azimuth joint. Thus, a clearance between the drive components is intended to be eliminated. The azimuth system can be traversed with an adjustable delivery rate by means of a second pump which is also connected to the hydraulic circuit. In the known device, a sumptuous hydraulic system is required in order to achieve a clearance elimination by two driving wheels, operated in opposite senses of rotation with respect to each other and sitting close to a toothed output wheel.
Starting from the state of the art explained above, the present invention is based on the objective to provide a method and a device of the kind mentioned in the beginning, by which a tightening of the adjustment devices is possible in a simple and inexpensive manner.